Axis 4-screw technique for occipital-cervical fixation in the treatment of atlantoaxial dislocation with axis osseous deformity: a retrospective study with a minimum 1-year follow-up.

Abstract

Objective: Atlantoaxial dislocation (AAD) with axis osseous deformity poses significant surgical challenges, particularly in complex anatomical cases. This study compares the efficacy of 2-screw versus 4-screw occipital-cervical fixation in improving neurological outcomes and reducing complications in patients with AAD and axis deformity.

Methods: A retrospective study was conducted on 37 patients with AAD and axis osseous deformity treated at the authors' institution from 2017 to 2023. The cohort included 19 patients treated with bilateral pars screws and translaminar screws (4-screw group) and 18 patients who received traditional pedicle screw (PS) fixation (2-screw group) prior to the application of 4-screw fixation. Radiographic parameters, including atlanto-dental interval (ADI), distance from the tip of the dens above the Chamberlain line (CL), cervico-medullary angle (CMA), and clivo-axial angle (CAA), were measured using radiography, CT, and MRI. Neurological function was assessed using the Japanese Orthopaedic Association (JOA) score. Data on complications and revision surgical procedures were collected and analyzed.

Results: Preoperative demographic and clinical characteristics were comparable between groups. Both techniques effectively improved CAA and CMA and reduced CL, but the 4-screw group demonstrated significantly lower ADI postoperatively (p = 0.001) and at the latest follow-up (p = 0.003). Patients in the 4-screw group also showed significantly higher JOA scores at the latest follow-up (p = 0.027), indicating better neurological recovery. The incidence of postoperative complications was lower in the 4-screw group (1 vs 6, p = 0.037), and no revision surgical procedures were required in this group, whereas 4 patients in the 2-screw group required further surgical interventions (p = 0.046).

Conclusions: Four-screw occipital-cervical fixation offers improved neurological functions and fewer postoperative complications compared to 2-screw fixation in patients with AAD and axis osseous deformity. This technique is particularly beneficial in cases with complex axis anatomy, suggesting its potential as a preferred alternative to traditional fixation methods.